Method for manufacturing a one-piece preform for a composite structure

ABSTRACT

A method for producing a one-piece preform for a composite structure includes the following steps: positioning a plurality of bundles of warp threads over two pairs of harnesses; making movements of low amplitude of each of the pairs of harnesses so as to make at least two adjacent and separate layers; and making movements of higher amplitude of the pairs of harnesses so as to at least partially link the at least two adjacent layers to an least one portion of the preform.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/FR2013/050609, filed on Mar. 21, 2013, which claims the benefit ofFR 12/52563, filed on Mar. 22, 2012. The disclosures of the aboveapplications are incorporated herein by reference.

FIELD

The present disclosure relates to a method for manufacturing a one-piecepreform for a composite structure, and to a weaving loom forimplementing such a method of producing.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

The producing of a composite structure comprises the assembling of areinforcement usually forming fibers providing the mechanical resistanceof the structure, and a matrix providing the cohesion of the structure.

In a known manner, the reinforcement may be formed by a fabric in twodimensions (2D) constituted by weft yarns woven with warp yarns, thisyarn for example achieved in carbon, Kevlar, or even glass.

The matrix is in a manner also known constituted by an organic ormineral resin. In the case of a matrix in resin for example, the methodfor manufacturing the composite piece will consist in a molding of thereinforcement layers, by Resin Transfer Molding (RTM), by Liquid resinInfusion (LRI), by Resin Film Infusion (RFI) or by any other method ofimpregnation or infiltration of resin, in dry fibrous elements.

A recurrent issue is linked to the mechanical resistance of this type ofstructure, frequently being subject to a delamination between thelayers.

A known solution consists in achieving a composite structure based on athree-dimensional reinforcement (2.5D or 3D) having a better mechanicalhold between the layers of fabric, with respect to an assembling of 2Dfabrics.

Typically, such a structure may have different types of weave(interlacing mode of the yarns) according to the selected weavingmethod. It is known for example as 3D weaving the weaving called“interlock” according to which several layers of warp yarns are wovenwith several layers of weft yarns, the whole able to be linked or not byat least one warp yarn called “reinforcing” which is added in thethickness of the fabric in order to link the different layers together.The mechanical resistance in particular, to delamination is higher withrespect to an assembling of 2D fabrics.

When the reinforcement is obtained, the operation aiming to give it thesought cohesion is achieved. It is necessary, before introducing thereinforcement in the mold for the resin injection, to give to thereinforcement a shape as close as possible to that which one wants toattain after achieving the cohesion operation. This operation ofpreparing the preform is accomplished for example thanks to cut-outs,foldings, etc. of certain parts of the preform. In order to achieve thisphase of preparing the preform, it is hence essential that the preformbe easily adjustable.

According to the methods of 3D weaving known from the prior art, thelayers of fabric are linked together in the direction of the thickness.

Hence, it is understood that the step of preparing the preform prior toinjection is in this case complex, since the folding is made impossiblebecause of the linking of the layers together, and that the cutting outof warp yarns highly affects the mechanical resistance of the finalcomposite structure.

A solution to these issues consists in achieving severalthree-dimensional preforms that are linked together for example bysewing, of “tufting” type, in particular, in order to give severalthicknesses to the final piece. This solution is not acceptable eitherfor the aforementioned reasons with reference to the 2D structures, themechanical hold between two preforms not being sufficient.

SUMMARY

The present disclosure relates to a method for producing a one-piecepreform for composite structure comprising said preform forming thereinforcement of the structure and a matrix, said preform being achievedby a three-dimensional weaving method thanks to a weaving loomcomprising at least one reed and at least two pairs of harnesses, eachof the harnesses comprising a plurality of heddles, each of the heddlesbeing equipped with a plurality of eyelets of which each one is intendedfor the passage of a warp yarn, the at least two pairs of harnessesbeing distributed at distinct altitudes from the weaving loom in such amanner as to form a plurality of levels, said method of producing beingcharacterized in that it comprises the following steps according towhich:

-   -   a plurality of bundles of warp yarns are positioned distributed        on the at least two pairs of harnesses;    -   we carry out alternatively and as desired:    -   movements of low amplitude of each of the at least two pairs of        harnesses for a predetermined warp yarn length, in such a manner        that, during the introduction of the weft yarns, at least two        adjacent layers are achieved, independent on at least one        portion of the preform;    -   movements of increased amplitude, with respect to said movements        of low amplitude, of the at least two pairs of harnesses, for a        predetermined warp yarn length, in such a manner that, during        the introduction of weft yarns the at least two adjacent layers        are at least partly linked on at least one portion of the        preform.

Thus, by providing a partial unlinking of the adjacent layers, theachieved preform may be adjusted manually prior to proceeding with thestep aiming to give cohesion to the preform.

According to other features, the method of producing according to thepresent disclosure, comprises an additional step to position on theweaving loom means for separating adjacent layers of the preform.

Thus, the forming of linkage between two adjacent layers is avoided.

More particularly, the means for separating the layers comprise at leasta stem that is positioned, as desired during the weaving, on the onehand between the reed and the pairs of harnesses, and on the otherbetween the adjacent layers.

According to a feature of the method of producing, at least one part ofa bundle of warp yarns is positioned on at least one level of pairs ofharnesses, in such a manner as to achieve during the introduction ofweft yarns a current section of the preform, and at least one bundle ofwarp yarns is positioned at a distinct altitude from a same harness insuch a manner as to achieve, during the introduction of weft yarns, atleast an extra thickness of the layer.

Thus, the thickness of the piece is varied punctually in such a manneras to create a hump in the direction of the warp yarn.

According to another feature of the method of producing according to thepresent disclosure, several warp yarns are disposed between two levelsof weft yarns.

This advantageously allows easily creating a groove in one of the layersof the preform.

Furthermore, the method of producing comprises a step of leaving atleast one weft yarn free in such a manner as to define a machining areawithout impact.

The method of producing according to the present disclosure alsocomprises an additional step to cut out and/or fold the preform in sucha manner as to give it a shape close to that sought to be given to thecomposite structure.

According to the present disclosure, the warp yarns and the weft yarnsare woven according to an interlock type weaving method.

The present disclosure also relates to a weaving loom for implementingthe method of producing according to the present disclosure,characterized in that it comprises a plurality of pairs of harnessesdisposed side by side in the weft direction, in such a manner as toallow an independent control of each of said harnesses.

Thus, by disposing several independent harnesses in the direction of thewidth of the preform, the different needs of the preform in terms ofthickness may be managed. The width of each of the harnesses correspondsto a width of extra thickness to be given to the preform.

The present disclosure still relates to a composite beam intended tosupport the sliding of at least one cowl of thrust reverser of aturbojet engine nacelle, said beam comprising at least onethree-dimensional preform and a cohesion matrix, and being characterizedin that said preform is the result of the method of producing accordingto the present disclosure.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 illustrates in isometric view the composite beam sought to beachieved;

FIG. 2 represents the preform in flat view sought to be obtained bythree-dimensional weaving;

FIG. 3 schematically represents the weave of the weaving, that is to saythe interlacing mode of the warp yarns and the weft yarns;

FIG. 4 represents a second interlacing mode of the warp yarns and theweft yarns;

FIG. 5 illustrates the preform represented in FIG. 2, one of the tabsbeing folded;

FIG. 6 illustrates the linkage between two layers of the preform;

FIG. 7 is similar to FIG. 6, according to another mode of linking layersof the preform;

FIG. 8 represents the shape obtained by the mode of linking the layersrepresented on FIG. 7;

FIG. 9 represents two layers of the preform, between which are set layerseparating means;

FIG. 10 illustrates the achieving of a hump in the warp direction C ofthe preform;

FIG. 11 represents the preform sought to be manufactured, of which theview is centered on the rails;

FIG. 12 illustrates the achieving of a groove during the weaving of thepreform;

FIGS. 13 to 15 show the steps of folding and cutting out of the preformresulting from the weaving method;

FIG. 16 illustrates a step of the method of producing according to thepresent disclosure, by which a non-perpendicular and unlinking of thewarp yarns is achieved;

FIG. 17 represents the preform of beam type, according to which thereinforcements are not perpendicular to the wall of the beam;

FIG. 18 details the machining area without impact of the preform.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

An aircraft is moved by several turbojet engines each housed in anacelle also accommodating a set of annex actuating devices linked tothe operating thereof and providing various functions when the turbojetengine is in operation or stopped. These annex actuating devicescomprise in particular, a mechanical system for actuating a thrustreverser, of which the role is to help with the braking of the aircraftduring landing.

A thrust reverser comprises one or several mobile cowls between, on theone hand, a deployed position in which they open in the nacelle apassage intended for the diverted flow, and on the other hand, aretractable position in which they close this passage.

The mobile cowl or mobile cowls slide along one or several beamscomprising rails in such a manner that when reversing during the openingphase, they uncover grids of jet vanes disposed in the thickness of thenacelle, the cold air flow crossing the nacelle thus discharged upstreamof the nacelle.

Certain passages of the description refer directly to such a beam fordescribing the method of producing according to the present disclosure,but in no case would this method be limited to this beam, but allows onthe contrary to achieve any type of woven preform for compositestructure, the hypothesis according to which the structure tomanufacture is a beam being simply adopted in order to make theunderstanding of the present disclosure easier.

FIG. 1 illustrates the beam in composite materials that are sought to beachieved.

As described before, a composite structure comprises a piece called“reinforcement”, which gives the final structure mechanical hold, and amatrix, usually resin-based, which provides the cohesion of thestructure.

The reinforcement structure is achieved according to the methodaccording to the present disclosure, according to which a one-piece 3Dpreform is manufactured woven by the weaving loom according to thepresent disclosure.

FIG. 2 illustrates the preform, flat, that is sought to be obtained as aresult of the 3D weaving.

The preform 1 comprises a tab 3 in its lower part, surmounted by anintermediate wall 5, then a current section 7.

The current section 7 comprises in its upper face 9 two tabs 11, ofparallelepiped shape, forming an extra thickness of the current section7. The tab 3, the intermediate wall 5, the current section 7 and thetabs 11 form sub-assemblies of the preform, which need to be achieved ina unitary manner, that is to say without having to add a sub-assemblywith respect to another sub-assembly. The achieving of such a one-piecepreform allows, as mentioned earlier, giving the final compositestructure a mechanical resistance higher than that obtained by areinforcement composed of multiple preforms.

The preform 1 is achieved by three-dimensional weaving, and comprises inthe direction of the length thereof warp yarns (according to directionC), and in the direction of the width thereof weft yarns (according todirection T).

The weaving weave, that is to say the interlacing mode of the warp yarnsand the weft yarns, is illustrated in FIG. 3.

FIG. 3 represents in longitudinal section (in the warp direction) anarea of the preform that has been achieved by 3D weaving.

The warp yarns 13 adopt a sawtooth shape over the entire length of therepresented area of the preform. Weft yarns 15 are set perpendicularlyto the warp yarns, in such a manner as to link the warp yarn together.

This type of interlacing of the warp 13 and weft 15 yarns of the preform1 is called interlock weaving.

The interlock armature is retained as an example in the description, butit goes without saying that the preform may be achieved by any othertype of armature, for example of “plain”, “twill”, “satin” type, etc.

According to another type of interlock weave, represented on FIG. 4, thewarp 13 and weft 15 yarns are not interlaced together, but warp yarnscalled reinforcement 16 yarns are introduced, crossing the preform inits thickness in order to maintain the weft yarns and the warp yarnstogether. The density of the reinforcement warp yarn 16 is variableaccording to the type of armature retained.

The sub-assemblies of the preform 1 may indifferently be achieved by anytype of armature of 3D fabrics, each of the sub-assemblies possibly ableto be achieved based on a different armature if the one skilled in theart finds it particularly useful.

Reference is made to FIGS. 2 and 5, respectively illustrating thepreform such as obtained as a result of the weaving method, and the samepreform in progress partly adjusted prior to resin injection.

It is required to fold over the tab 3 so that it is substantiallyperpendicular to the intermediate wall 5, as represented on FIG. 5.

It is understood that given that it is sought to achieve the preform inone single piece, the tab 3 and the wall 5 must only partly be linkedtogether, in order to be able to handle each of these sub-assembliesindependently from each other on the non-linked part.

FIG. 6 illustrates in longitudinal section the manner in which the loweradjacent layers 17, forming the tab 3, and upper 19, forming the wall 5,have been woven thanks to the method according to the presentdisclosure.

The layers 17 and 19 comprise a plurality of warp 13 and weft 15 yarns.The layers 17 and 19 are independent on the portions 21 a and 21 b andare linked together on the portion 23.

The weaving loom allowing this type of partial linkage comprises aplurality of pairs of harnesses, disposed at different altitudes of theweaving loom, forming a plurality of levels.

More particularly, a harness typically comprises two frames linked andseparated by heddles. Each heddle comprises a plurality of eyelets inwhich the warp yarns are introduced.

It is considered that the weaving loom comprises two levels ofharnesses, that is to say a pair of lower harnesses and a pair of upperharnesses.

The warp yarns 13 are inserted at the beginning of the method of weavingin the eyelets the pair of lower and upper harnesses.

The lower and upper harnesses are put in movement in such a manner as tocreate, during the introduction of the weft yarn 15, the lower 17 andupper 19 adjacent layers, independently from each other, obtained by alimited amplitude of the harness movement.

It is managed to punctually link these two adjacent layers bytemporarily increasing the amplitude of the harnesses with respect tothe amplitude retained for achieving the distinct layers. Weft yarn isalso set over the entire thickness of the preform at the portion 23.

Thus, the adjacent layers 17 and 19 are made independent on the portions21 a and 21 b and linked together on the portion 23, thus allowing toachieve a folding, for example manual or using a specific externalmachine, of the tab 3 with respect to the wall 5.

The amplitude of the movements of the harnesses may be variable duringweaving, in such a manner as to allow the achieving of hollow shapes ofdifferent thicknesses.

For example, according to one form represented on FIG. 7, the amplitudeof the movement of the harnesses is reduced on a portion 25, on whichthe weft yarns are no longer set, in such a manner as to form a hollowarea 27. The skilled person completes by symmetry in such a manner as toobtain the piece represented on FIG. 8.

The adjacent layers are of identical and constant thicknesses such asrepresented on FIG. 8. However, it is possible to achieve adjacentlayers of distinct and progressing thickness thanks to the method ofproducing according to the present disclosure.

This disposition is advantageous as the preform may be equipped in thishollow area with a tool-piece allowing to achieve an opening in thefinal composite structure. This hollow area may also be of interest whenit is sought to integrate within the final composite structure a foam ora honeycomb type core, for example, advantageously allowing to improvethe mechanical resistance of the final piece, in particular incompression.

According to another form of the method according to the presentdisclosure, represented on FIG. 9, means for separating layers 17 and 19are set.

The separating means comprise, as represented on FIG. 9, a stem 28 thatis disposed between the reed of the weaving loom (not represented) andthe harnesses (not represented), and between two independent adjacentlayers 17 and 19. Thus, it is provided that the warp yarns of one of thelayers 17 or 19 are not linked inadvertently with the weft yarns of theother of the layers 17 or 19.

It is now referred to FIG. 10, illustrating the achieving of a hump inthe warp direction C of the preform.

It is initially provided the harnesses of warp yarns 13 that aredisposed in such a manner as to define, during the introduction of weftyarns 15, the layer 17 corresponding to the current section of thepreform.

It is also disposed the harnesses of warp yarns 29, disposed at distinctaltitude of the warp yarns 13.

It is achieved such a hump in the warp direction C by temporarilysetting during the weaving weft yarns 30 on a thickness 31 distinct fromthe layer 17 which defines the current section.

The weaving loom comprises a plurality of pairs of harnesses disposedside by side in the weft direction, in such a manner as to allow anindependent control of each of said harnesses.

This prevents that the introduction of weft yarns causes to define anextra thickness of the current section over the entire width of thepreform.

Thus, the width of a pair of harnesses corresponds to widths of theextra thicknesses that are sought to be given to the preform. Thus, itis made possible to introduce weft yarn which will be linked to thestructure only on the predetermined widths of the preform in such amanner as to achieve an extra thickness on a predetermined width.

By way of example, and by referring again to FIG. 2, to each of theextra thicknesses 11 corresponds a pair of harnesses, of which the widthof a pair of harnesses is substantially equal to a width L of an extrathickness.

For a considered level, the weaving loom comprises as many pairs ofharnesses as required, each of the pairs corresponding to a layer width.

Thus, it is achieved as desired extra thicknesses of the currentsection, of which the width is variable as desired.

In the considered example, the extra thicknesses 11 of the currentsection 7 are intended to provide the function of rails 32 of the beam,visible on FIG. 11, along which the thrust reverser cowl will slide.

The rails 32 are subjected to mechanical forces during the sliding ofthe cowl, and the method of producing according to the presentdisclosure, which allows achieving the preform in one single part, isparticularly advantageous for providing the piece with the requiredmechanical hold.

It must be understood that such levels of mechanical requirements cannotbe reached by method of producing a preform according to the prior art,according to which the rails are inevitably constituted by preformsadded to the main preform.

Finally, according to another step of the method of producing accordingto the present disclosure, it is disposed several warp yarns 13 betweentwo levels of weft yarns 15, as illustrated in FIG. 12.

The warp yarns 13 are packed by the weft yarns 15, thus allowing tocreate a groove.

It is possible, during the achieving of certain pieces, to combineseveral of the aforementioned weaving methods, on the one hand in orderto limit the additional steps of fashioning the preform, and on theother hand in order to prevent the assembling of multiple preforms,which affect the mechanical features of the final composite structure.

Reference is now made to FIGS. 13 to 15, illustrating the steps to beachieved in order to attain the required shape.

It is attained the shape of the preform such as illustrated in FIG. 14thanks to a step of folding the current section 7 of the preform, alonga line 33.

Then, in order to achieve the reinforcements 34, it is first achieved anoperation of cutting out the intermediate wall 5, along lines 35 a, 35b, 35 c, 35 d. Then, each of the two parts resulting from the cuttingout of lines 35 a, 35 b, 35 c, 35 d is folded over. Thus, thereinforcements 34 are obtained.

Advantageously, these reinforcements are achieved based on the preform1, without having to add an additional piece, thus allowing to obtaingood mechanical features of the final composite structure.

Then, the reinforcements 34 are cut out in order to give them theirfinal shape, such as represented on FIG. 15.

Then, it is attained, after these steps of cutting out and folding theportions of the preform 1 resulting from the method of producingaccording to the present disclosure, a one-piece three-dimensionalpreform close to the shape of the final composite structure.

The warp yarns which are not assembled with weft yarns after the weavingmethod are cut out.

It is now referred to FIG. 16, illustrating a step of the method ofproducing according to which it is achieved a non-perpendicularunlinking of the warp yarns.

The stem 28 is mounted moveable in translation on the weaving loom in adirection parallel to that of the warp direction, and slides duringweaving. This prevents the linkage of the 2 adjacent layers 17, 19 onthe totality of the width of the fabric where the stem is found.

According to an alternative (not represented on the figures), in orderto obtain a linking or a parallel unlinking, it is provided two stemseach positioned at an end of the linked part of the preform. The stemsare mounted moveable in translation on the weaving loom, and move in adirection parallel with that of the warp direction, in the oppositedirection.

In the example of producing of the preform of beam type, represented onFIG. 17, the reinforcements 34 should not be perpendicular to the wall 5of the beam. For this, the interlock links are stopped angled thanks tothe stem.

According to another aspect of the method of producing according to thepresent disclosure, the preform may also be subject to a machining inorder to achieve piercings 36, visible in particular, on FIG. 15.

According to an aspect of the present disclosure, it is provided in thepreform a portion only provided with weft yarns.

In reference to FIG. 18, it is achieved by the method of producingaccording to the present disclosure a machining area without impact 37,corresponding to a portion of the layer in which the weft yarns are leftfree, allowing to not affect the tops 39 of the warp yarns 13 during apiercing operation.

Thanks to the method according to the present disclosure, it is possibleto manufacture a one-piece three-dimensional woven preform, partlynon-linked in the warp direction, which can be advantageously adjustedin order to form the reinforcement of a composite structure.

Thus, it is no longer necessary to achieve multiple preforms, of whichthe links do not have a good mechanical hold.

It is worth noting that the preform described in the present disclosuremay be achieved indifferently by replacing the warp yarns by the weftyarns, and by replacing the weft yarns by the warp yarns. Thissubstitution may allow saving time for the manufacture of the preform ora decrease in the loss of material.

It may also be interesting to invert the weft yarns and the warp yarnsaccording to the nature of the weaving loom, or according to thetechnical constraint linked to the geometry of the piece to manufacture.

As it goes without saying, the method of producing is no way limited tothe producing of a preform of a beam for thrust reverser, this examplehaving been described solely for the purpose of illustrating theimplementation of the method, but on the contrary applies to anythree-dimensional weaving method.

What is claimed is:
 1. A method for producing a one-piece preform forcomposite structure comprising said one-piece preform forming areinforcement of the composite structure and a matrix, wherein saidone-piece preform is achieved by a three-dimensional weaving methodusing a weaving loom, and the weaving loom comprises at least one reedand at least two pairs of harnesses, each of the harnesses comprising aplurality of heddles, and each of the heddles being equipped with aplurality of eyelets of which each one is a passage of a warp yarn, theat least two pairs of harnesses being distributed at distinct altitudesfrom the weaving loom so as to form a plurality of levels, said methodcomprising the following steps: positioning a plurality of bundles ofwarp yarns on the at least two pairs of harnesses; movements of lowamplitude of each of the at least two pairs of harnesses for apredetermined length of said warp yarns, in such a manner that, duringan introduction of weft yarns, at least two adjacent layers areachieved, independent on at least one portion of the one-piece preform;and movements of increased amplitude, with respect to said movements oflow amplitude, of the at least said two pairs of harnesses, for apredetermined length of said warp yarns, in such a manner that duringthe introduction of the weft yarns, the at least two adjacent layers areat least partly linked on at least one portion of the one-piece preform.2. The method for producing a one-piece preform for composite structureaccording to claim 1, further comprising a step of positioning on theweaving loom means for separating the adjacent layers of the one-piecepreform.
 3. The method for producing a one-piece preform for compositestructure according to claim 2, wherein the means for separating theadjacent layers comprise at least one stem that is positioned, duringthe weaving, between the at least one reed and the at least two pairs ofharnesses, and between the adjacent layers.
 4. The method for producinga one-piece preform for composite structure according to claim 1,wherein at least one part of the bundles of warp yarns is positioned onat least one level of the at least two pairs of harnesses so as toachieve, during the introduction of the weft yarns, a current section ofthe one-piece preform, and at least one bundle of warp yarns ispositioned at a distinct altitude from a same harness so as to achieve,during the introduction of weft yarns, at least an extra thickness ofone of the two adjacent layers.
 5. The method for producing a one-piecepreform for composite structure according to claim 1, wherein severalwarp yarns are disposed between two levels of the weft yarns.
 6. Themethod for producing according to claim 1, further comprising a step ofleaving at least one weft yarn free so as to define a machining areawithout impact.
 7. The method for producing a one-piece preform forcomposite structure according to claim 1, further comprising a step ofcutting out and/or folding the one-piece preform so as to give a shapeclose to a shape to be given to the composite structure.
 8. The methodfor producing a one-piece preform for composite structure according toclaim 1, wherein the warp yarns and the weft yarns are woven accordingto an interlock type weaving method.
 9. A weaving loom for implementingthe method of producing according to claim 1, further comprising aplurality of pairs of harnesses disposed side by side in the weftdirection so as to allow an independent control of each of saidharnesses.